The problems associated with the flammability of flexible polyurethane foamed plastics are matters of acknowledged repeatable documentation of fires that became catastrophic because of the fueling and spreading effects of their pyrolyzed products which were readily meltable and readily combustible. The potential hazards of uncontrollable flammability have been compounded by the ubiquitous applications of these materials to household, industrial, aircraft, and military uses where low density, soft, flexible and compliant products are desired for insulation, bedding, cushions, furniture padding, etc.
To reduce the flammability and flame-propagation properties of these polyurethanes, selected flame-retardants of the type noted in my patent U.S. Pat. No. 4,061,605 titled "Reaction Products of Benzenephosphonic Acid and Melamine as Flame-Retardant Additives" may be incorporated as part of the foaming mixture. Although this is a practical, efficient insitu procedure for utilizing these "additives", their properties of limited aqueous solubilities and pronounced thickening and incipient gelling in water dictates against the suitability of aqueous solutions of these salts for the post-treatment of the foamed plastics in question.
The post application of a combination of modified benzenephosphonic acid/melamine salts (processed in accordance with the disclosure of this invention) and a film-forming latex as a carrier (in which the polymeric deposit is soft, flexible, and intrinsically flame-resistant) meets the objective of reducing involvement of the foamed plastic towards intensifying or propagating a fire following exposure to an igniting source such as a free flame, without unduly compromising the necessary physical properties of compressibility and flexibility inherent to their aforementioned uses.
Modification of the benzenephosphonic acid/melamine flame-retardants to the extent that they remain compatible when added to a selected latex carrier, is accomplished by increasing the pH of their acidic aqueous thickened states to a value from approximately 8 to 10 by the addition of ammonium hydroxide. Subsequent drying of the treated foamed plastic essentially restores the original physical properties of the retardant-salts that remain within the matrix of the polymeric carrier.
As objects of this invention, it is intended that: the applicability of the benzenephosphonic acid/melamine salts for the post-treatment of flexible polyurethane foamed plastics be disclosed; the procedure be delineated for the ammoniated modification of these flame-retardant salts; the preferred limits for the flame-retardant salts and the polymeric carrier be set-forth; an applicable, flame-resistant polymer latex carrier be described and identified; procedures for the post-treatment of the flexible polyurethane foamed plastics, using the ammoniated stabilized flame-retardant/latex carrier compositions of this invention, be presented that result in products that are substantially inert to flame-propagation after free flame exposure. These and other objectives and advantages will be apparent from the described concepts and results.